magnification, resolution and illumination
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Magnification, Resolution and Illumination
Cell Biology: Magnification and Illumination
Let's take a look at the secret life inside our cells...
How large are cells?Let's put things into perspective....
Size is relative….Organism Size
Prokaryotic cell 1 – 10 μmAnimal Cell 10 – 30 μmPlant Cell 10 – 100 μm
Virus < 100 ηmDNA molecule 2 ηmPhospholipid membrane
10 ηm
Is magnification all that matters?Magnification versus Resolution
Is there a limit to magnification?Does magnification improve resolution?Resolution of a microscope is its ability to separate small
objects which are cose togetherResolution is determined by light/(electron) wavelength;
the shorter the wavelength, the higher the resolutionLight microscope resolution is 0.2 μmElectron microscope resolution is 1 ηmScanning Tunnel microscope resolution is 0.01 ηm
length 0.01 ηm depth
Light microscope: Magnification
Normal maximum
magnifications of ocular and
objective lenses are 10X and
100X respectively, giving overall
maximal magnification of
X 1000
Why do modern microscope images look so beautiful?
Modern Illumination techniques used in light microscopy
These techniques modify the light path to generate improved contrast: Phase contrast micrcoscopy Cross-polarised (confocal) light microscopy Dark field microscopy Fluorescent microscopy
Phase contrast microscopy Improved contrast,
allowing identification of structures in living cells
Allowed us to understand cell division
Won its inventor, Franz Zernike, the NOBEL PRIZE in 1951
Nobel Prize link to Phase microscope:
Phase Nobel
Contrast Microscopy Fluorescence contrast
techniques Immunofluorescence
techniques Here is a whole gallery of
beautiful images: Fluorescence Gallery Cell fluorescence
Electron Microscopy! Follows the same
principles as light microscopy, but shines a beam of electrons rather than light particles
The lower ‘wavelength’ of the electron beam allows incredible resolution
Can visualise particles to the order of a few angstom (10-10m)
Transmission Electron Microscopy
Wellcome scanning microscope
Designed by Ernst Ruska (Heidelberg) in 1938
He won the Nobel Prize just before his death, in 1986
First electron microscope was built in Toronto in 1938
Scanning Electron Microscope
Scanning Electron microscope
Scanning Tunneling Microscope
Sharing a Nobel Prize Scanning tunneling micr
oscopes
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